Why dentists may have rats to thank


Image of rat teeth from Scienceline (credit:  The International Rice Research Institute, flickr.com) Image of rat teeth from Scienceline (credit: The International Rice Research Institute, flickr.com)

What does tooth decay have to do with rats? For Neandertals, tooth decay was a rare occurance. Research suggests that tooth decay became more prominent with the development of agriculture. Dr. Ordaz, Stanford School of Medicine, and colleagues analyzed common strains of bacteria (Streptococcus mutans) responsible for causing cavities. They found that the bacteria began expanding exponentially around 10,000 years ago, similar to the dawn of agriculture. The authors suggest that as humans and rats were brought closer together with agriculture, humans became exposed to the bacteria (Streptococcus ratti) responsible for causing tooth decay in rodents, which also happens to be closely related to S. mutans.

Research on fossilized skeletons from Wadi Halfa, Sudan also supports a link between agriculture and tooth decay. In this study, Dr. George Armelagos from Emory University showed that the incidence of cavities increased from 0.8 to almost 20 percent when the Nubian people switched to agriculture. Similarly, other researchers suggest that the increased prevalence of tooth decay may be caused by a change in the diet, more carbohydrate intake, as opposed to the theory that tooth decay arose from our close proximity to rats.


Cornejo OE, Lefebure T, Bitar PDP, Lang P, Richards VP, Eilerston K, Do T, Beighton D, Zeng L, Ahn S, Burne RA, Siepel A, Bustamante CD, Stanhope MJ.  Evolutionary and Population Genomics of the Cavity Causing Bacteria Streptococcus mutans. Mol Biol Evol. 2012. doi: 10.1093/molbev/mss278

Greene DL, Ewing GH, Armelagos GJ. Dentition of a mesolithic population from Wadi Halfa, Sudan. Am. J. Phys. Anthropol., 27: 41–55. doi: 10.1002/ajpa.1330270107

Scientific American

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By Jim Thomerson (not verified) on 23 Feb 2013 #permalink

Well! Dr. Dolittle, I am amazed by seeing the teeth size of this rat..Yes tooth decay is on spree !

This information is a very big help to the people. At least we know when this so called tooth decay began.

This is quite intriguing, I believe it was great back then during the period of neanderthals since they had no cavities but what strikes me is that those people didn't brush their teeth as far as I know and their water had no flourine. We have toothpastes and our water contains flourine yet we experience tooth decay? Aren't these advancements in technology supposed to help us in any way? and thank you for enlightening us that we have close proximity with rats that is new knowledge to me. Keep up the good work Dr Dolittle.